Treatment of some medical conditions involves administering a drug (or a combination of drugs) subcutaneously or intravenously into a patient.
A drug delivery system can be divided in two parts, namely a device for supplying the drug (such as a bag, pump or syringe) and a tubing arrangement for delivering the drug into the patient.
The tubing arrangement includes a soft cannula, which can also be referred to as a catheter. One end of the cannula is inserted into the patient, leaving the other end available for connection to the drug-supplying device. The cannula is held in place by taping the cannula to the surface of the skin of the patient or by using a housing which itself is attached to the surface of the skin.
To insert the cannula into the patient, a device is used which employs an introducer needle, for example as described in U.S. Pat. No. 5,522,803. The cannula is carried on the needle such that, when the needle pierces the skin and underlying tissue, the cannula is also inserted. The needle is then withdrawn, leaving the cannula in place.
Existing insertion devices suffer the drawback that the needle is often exposed before and/or after insertion, thereby allowing possible contamination of the needle and exposing the operator to so-called “needle stick” injury, which carries with it a risk of infection.
The present invention seeks to provide an improved cannula insertion device which reduces the possibility of injury.
In the prior art arrangement described in U.S. Pat. No. 5,522,803, once the cannula has been inserted into the patient, the inserter needle is withdrawn by disconnecting an inserter hub from the cannula housing and attaching a connecting hub in its place. The connecting hub includes a hollow needle which pierces a membrane (or “septum”) in the cannula housing.
However, the prior art connecting hub suffers at least two drawbacks. Firstly, the hollow needle on the connecting hub is itself a potential hazard and could lead to needle stick injury. Secondly, the connecting hub can be difficult to align and orientate with the cannula housing.
The present invention seeks to ameliorate one or both of these problems.
The prior art arrangement described in U.S. Pat. No. 5,522,803 does not describe how ancillary medication can be delivered through the same access site. One possible solution is to disconnect the tubing, insert a needle through the septum and inject. However, this arrangement only allows one fluid to be delivered at a time. Another solution is to provide a multi-port device upstream. However, this can be inconvenient for the patient since such a device can restrict mobility. Moreover, the line between the cannula housing and multi-port device may need to be flushed. The longer the line, the greater the amount of fluid required for flushing. Furthermore, the arrangement requires additional connectors.
The present invention seeks to ameliorate at least one of these problems.